U.S. patent number 5,960,670 [Application Number 08/571,156] was granted by the patent office on 1999-10-05 for actuator for gear transfer case with cushion at end of travel.
This patent grant is currently assigned to Ut Automotive Dearborn, Inc.. Invention is credited to Anthony Iverson, Ronald L. Merckling.
United States Patent |
5,960,670 |
Iverson , et al. |
October 5, 1999 |
Actuator for gear transfer case with cushion at end of travel
Abstract
A vehicle transfer case for movement between two- and four-wheel
drive includes a stop cushion as an end of travel range is
approached. The cushion is preferably provided by a generally
U-shaped spring that is contacted by the stop at either of its ends
of travel. The cushion prevents the stop from locking into a
housing for the gear.
Inventors: |
Iverson; Anthony (Monroe,
MI), Merckling; Ronald L. (Macomb Township, MI) |
Assignee: |
Ut Automotive Dearborn, Inc.
(Dearborn, MI)
|
Family
ID: |
24282532 |
Appl.
No.: |
08/571,156 |
Filed: |
December 12, 1995 |
Current U.S.
Class: |
74/337.5;
180/233; 180/247; 74/526 |
Current CPC
Class: |
F16H
35/00 (20130101); F16H 63/304 (20130101); Y10T
74/2063 (20150115); F16H 2063/3056 (20130101); Y10T
74/19279 (20150115); F16H 2035/006 (20130101) |
Current International
Class: |
F16H
35/00 (20060101); F16H 63/30 (20060101); F16H
059/00 () |
Field of
Search: |
;74/335,337.5,526
;180/233,247 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4664217 |
May 1987 |
Welch et al. |
4805472 |
February 1989 |
Aoki et al. |
4841793 |
June 1989 |
Leigh-Monstevens et al. |
4843901 |
July 1989 |
Peterson et al. |
5150637 |
September 1992 |
Ninomiya et al. |
5407024 |
April 1995 |
Watson et al. |
5409429 |
April 1995 |
Showalter et al. |
5469757 |
November 1995 |
Buhl et al. |
|
Primary Examiner: Jeffery; John A.
Assistant Examiner: Fenstermacher; David
Attorney, Agent or Firm: Howard & Howard
Claims
We claim:
1. A motor and transmission assembly comprising:
a reversible electric motor driving a worm having a thread;
a worm gear having gear teeth engaged with said thread on said
worm, a stop selectively engaging a stop surface preventing
rotation of said worm gear beyond two ends circumferentially spaced
by less than 360.degree.; and
a cushion for cushioning said stop as said stop approaches said
stop surface at said ends.
2. An assembly as recited in claim 1, wherein said cushion is
provided by a spring which is contacted by said stop as said stop
approaches said ends.
3. An assembly as recited in claim 2, wherein spring cushions are
disposed at opposed circumferential locations and associated with
each of said ends.
4. An assembly as recited in claim 3, wherein a single spring
provides both cushions.
5. An assembly as recited in claim 4, wherein said spring is
received in a stop surface which extends from said surface of a
housing which mounts said worm gear.
6. An assembly as recited in claim 5, wherein said stop surface
includes a channel receiving an apex of said spring, said spring
cushions defined by opposed ears extending from said apex.
7. An assembly as recited in claim 6, wherein said ears extend away
from sidewalls of said surface for providing said cushions.
8. An assembly as recited in claim 1, wherein a position feedback
member monitors the position of said worm gear.
9. An actuator for a transfer case of a vehicle comprising:
a motor for driving a first gear, said first gear engaging a second
gear and being driven by said first gear;
a shaft being driven by said second gear, said shaft moving an
actuator for a transfer case of a vehicle, the rotational position
of said shaft causing movement of said actuator to achieve a
selected mode of operation for a transfer case;
said second gear being prevented from rotating 360.degree., and
having a range of travel with two circumferential end spaced by
less than 360.degree., a stop provided on said second gear member
to prevent movement beyond said ends; and
a cushion to be contacted by said stop as said stop approaches each
of said ends, and providing a cushion for said stop.
10. An actuator as recited in claim 9, wherein said cushion is
provided by a spring which is contacted by said stop as said stop
approaches said ends.
11. An actuator as recited in claim 10, wherein spring cushions are
disposed at opposed circumferential locations and associated with
each of said ends.
12. An actuator as recited in claim 11, wherein a single spring
provides both said cushions.
13. An actuator as recited in claim 12, wherein said spring is
received in a stop surface extending from a surface of a housing
which mounts said second gear.
14. An actuator as recited in claim 13, wherein said stop surface
includes a channel receiving an apex of said spring, said spring
cushions defined by opposed ears from said spring and extending
from said apex.
15. An actuator as recited in claim 14, wherein said ears extending
away from sidewalls of said surface for providing said cushion.
16. An actuator as recited in claim 9, wherein there is a groove in
said shaft and said actuator is a pin which moves within said
groove between a plurality of axial positions to achieve said
selected mode of operation for said transfer case.
17. An actuator as recited in claim 9, wherein said first gear is a
worm and said second gear is a worm gear.
18. An actuator as recited in claim 9, wherein a position feedback
member is disposed for monitoring the position of said second
gear.
19. A method of operating an actuator for a vehicle transfer case
comprising the steps of:
(1) providing a motor driving a first gear, said first gear
engaging a second gear, said second gear driving a shaft, said
shaft controlling movement of an actuator pin to move a vehicle
transfer case between positions providing two- or four-wheel drive
for a vehicle;
(2) operating said motor to drive said second gear to move said
actuator pin to desired positions, the rotation of said second gear
being limited to a range of less than 360.degree.; and
(3) providing a spring cushion to cushion movement of said second
gear as it approaches the end of its range of travel.
20. A method as recited in claim 19, wherein said cushion is
provided by a spring.
Description
BACKGROUND OF THE INVENTION
This Application relates to a transmission for driving a vehicle
transfer case actuator wherein a cushion is provided for a stop
which prevents movement of the transmission beyond desired ends of
travel.
In the prior art, transfer cases allow vehicles to be switched
between two-wheel and four-wheel drive modes of operation. In
addition, transfer cases typically allow both high and low gear
ratios in both two- and four-wheel drive modes.
It has been standard that an actuator assembly moves shift collars
between locations to drive one or two axles and engage either the
high or low gear ratios. The actuator assembly has typically
included a motor driving a worm. The worm engages a worm gear, and
a shaft is driven by the worm gear. An actuator pin is driven by
the shaft between several positions at which the various drive
modes are obtained.
In one example, the worm drives the worm gear through a range of
approximately 270.degree.. A groove in the driven shaft moves an
actuator pin between any one of four distinct axial positions. In
the distinct axial positions, the actuator pin moves shift collars
between locations wherein one axle or two axles are driven, and
also between high and low gear ratios. Thus, by selectively
rotating the worm gear, one can move the actuator pin to a desired
location and achieve a particular drive mode. The motor is
preferably a reversible motor such that the pin can be moved back
and forth between the positions.
Problems have arisen in the prior art with such transmission. In
particular, it would be undesirable to allow the shaft to rotate
360.degree.. Such rotation could lock the transfer case members and
prevent movement of the shift collars or actuator pin. To that end,
stops have typically been provided on the worm gears to prevent
rotation from approaching 360.degree.. In one prior art example, a
stop pin extends axially from a face of the worm gear and contacts
a stop surface within the worm gear housing. In this way, the stop
pin prevents the gear from even approaching 360.degree. of
rotation.
In the prior art systems, a smaller degree of angular motion is
typically required to achieve the required movement of the actuator
pin. In theory the worm gear should never approach the extremes of
the stop. As one example, in the prior art systems, only
270.degree. of rotation is necessary to actuate or move the
actuator pin, while the motor transmission has 330.degree. of
range. A position feedback sensor monitors the position of the worm
gear and should stop rotation at the extremes of the 270.degree.
range. However, in practice it does happen that the motor
occasionally moves beyond the 270.degree. range. In such
circumstances, without a stop, the motor would extend up to
360.degree. of rotation. The motors typically incorporated into the
use systems allow full rotation, as a limited rotation motor is
unduly expensive. For that reason, the prior art has typically
included a stop to prevent rotation beyond a greater range (i.e.
330.degree. of rotation). Thus, as the transmission approaches
330.degree. of rotation, the stop will prevent further rotation. In
the past, the stop often wedges into the housing structure and
locks the gear motor. Once this happens, the system is no longer
functional.
SUMMARY OF THE INVENTION
In a preferred embodiment of this invention, a transmission for
driving the actuator in a transfer case includes a worm gear driven
by a worm. A stop on the worm gear is provided with a cushion as it
approaches its end of travel, and before it hits the stop surface.
Thus, the stop will not wedge into the housing, thus locking the
worm gear. It is preferred that the worm gear drives a shaft
including a groove that moves an actuator pin between selected
axial positions. Movement of the actuator pin causes movement of
corresponding shift collars to result in the selection of two-wheel
or four-wheel drive, and also high and low gear ranges. The
structure for achieving the two- and four-wheel drive and high and
low ratios forms no portion of this invention, and is shown
schematically in this Application.
In preferred embodiments of this invention, the stop contacts a
spring which provides the cushion as it approaches its end of
travel. In a most preferred embodiment the spring is generally
U-shaped, and has sides extending from opposed circumferential
locations such that it provides a stop cushion for the stop when
moving in either rotational direction. In a most preferred
embodiment, a housing for the worm gear includes a stop wall with a
spring channel. The U-shaped spring is received in the channel with
spring sides extending outwardly in both directions. The sides
provide cushions as the stop approaches either end of travel. In
this way, the stop is prevented from wedging into the wall thus
locking the worm gear.
In a method according to the present invention, a cushion is
provided to cushion a stop for a worm gear in a transfer case
actuator as the worm gear approaches its end of travel. In a
preferred method, the cushion is provided by a spring as described
above.
These and other features of the present invention can be best
understood from the following specifications and drawings, of which
the following is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a transfer case actuation system.
FIG. 2 is a top view of a housing for a worm gear in the system
shown in FIG. 1.
FIG. 3 is a cross-sectional view through the housing and worm gear
of the present invention.
FIG. 4 is an enlarged view of a portion of the housing illustrated
in FIG. 2.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
A transfer case actuation system 20 is illustrated in FIG. 1. A
motor 22, which may be a DC motor selectively drives a worm 24.
Worm 24 engages teeth on a worm gear 26. Motor 22 is preferably
reversible, and upon rotation of worm 24, the worm gear 26 rotates.
Worm gear 26 drives a shaft 28. As shown schematically, shaft 28
may include a cam groove 30. Actuator pin 32 is received within cam
groove 30. A shift collar system 34 is shown schematically being
driven by pin 32. As known, upon rotation of the shaft 28, the cam
groove 30 causes axial movement of pin 32, and thus movement of
collar 34 between several axial positions. The positions are shown
schematically in this Figure, and the structure of the groove 30,
the pin 32, and the collar system 34 form no portion of this
invention. Upon movement of the collar system 34 between the
several positions, gearing is moved between two- and four-wheel
drive positions, and also between high and low gear ratios. The
rotation of the shaft 28 does not require 360.degree. to achieve
all of the required movement of the actuator pin 32. In fact, it
would be undesirable to have 360.degree. of rotation.
In the prior art, it is typical that only about 270.degree. of
rotation is required to achieve all movement of the actuator pin
32. The motor 22 typically can rotate through 360.degree.. The
transmission between worm 24 and worm gear 26 is such that the
rotation is limited to prevent rotation through 360.degree., as
such rotation would be undesirable. To that end, some stop has been
provided in the prior art to prevent rotation of the worm gear 26
as it approaches about 330.degree. of rotation. Typically, more
rotation is allowed than is required by the 270.degree. of rotation
to move the pin 32 as necessary.
A position feedback member 35 is shown schematically, and monitors
the movement of the worm gear 26. Position feedback member 35 is
associated with the control for motor 22, and also for the overall
transfer case system. A housing 36 receives the worm gear 26 and
position feedback member 35.
In theory, position feedback member 35 should prevent rotation of
worm gear 26 beyond the 270.degree. of rotation necessary for
operation of actuator pin 32. In practice, however, it sometimes
occurs that the feedback position member 35 does not stop further
rotation of worm gear 26. This has required the stop as utilized in
the prior art. It should be understood that the 270.degree. and
330.degree. ranges are examples, and that the actual number may
differ.
As shown in FIG. 2, housing 36 also receives worm gear 26 and worm
24. A stop surface or wall 38 extends from a floor of housing 36. A
stop cushion spring 40 is associated with stop surface 38, and
provides a cushion for a stop member 42 that extends downwardly
from a face of worm gear 26. The worm gear 26 is partially
fragmented away to show the detail of surface 38 and spring 40. As
worm gear 26 is rotated through the 330.degree. of range of
rotation by worm 24, stop 42 moves toward spring 40 as shown in
FIG. 2. When worm 24 is rotated in the reverse direction, the stop
42 will rotate with the worm gear 26 through approximately
330.degree. such that it contacts an opposed side of spring 40. The
spring 40 provides a cushion for movement of the stop 42 as it
approaches its ends of travel. As such, the stop 42 is not wedged
into the stop surface 38 such that it may lock further rotation of
the worm gear 26.
As shown in FIG. 3, the housing 36 includes a generally U-shaped
spring 40 received within stop surface 38. The spring 40 includes
sides 44 connected at an apex 46. Remote ends 48 are also received
in the stop surface 38. As shown, a first generally V-shaped
channel 50 receives the apex 46 and extends towards the sides 44. A
second channel portion 49 is formed in the stop surface 38 and
receives the remote ends 48.
Ears 52 of the spring 40 extend outwardly away from a sidewall 54
of the stop surface 38. Now, as the stop 42 approaches its extreme
of travel, it begins to contact the ear 52 as shown in FIG. 2. The
spring ear 52 begins to be compressed towards the sidewall 54,
however a resistance is also created to further movement of the
stop 40. Spring ear 52 thus provides a cushion preventing the stop
42 from being wedged into the surface of the stop surface 38,
thereby locking the worm gear. The inventive use of the spring
provides a cushion that allows the stop 42 to approach its ends of
travel without damage to the overall transmission or actuator
system 20.
As shown in FIG. 4, spring 40 and stop 42 are sized such that the
stop 42 will contact spring 40. As set forth in the other figures,
once stop 42 begins to contact spring 40, resistance to further
rotation is applied by the spring 40.
In a method of operating a transfer case actuator according to this
present invention, a cushion is provided to cushion movement of a
stop member on a worm gear as that worm gear approaches its extreme
travel range. The cushion is preferably a spring member, as
described above. During operation of the system, the stop will
typically not approach its extreme travel range, however when it
does the stop encounters the cushion against further movement of
the stop.
A preferred embodiment of this invention has been disclosed,
however, a worker of ordinary skill in the art would recognize that
certain modifications would come within the scope of this
invention. For that reason, the following claims should be studied
to determine the true scope and content of this invention.
* * * * *